1. Field of the Invention
The present invention relates to a method of controlling a fusing speed of an image forming apparatus. More particularly, the present invention relates to a method of controlling a fusing speed of an image forming apparatus, which controls a conveying speed of a sheet of paper when the fusing speed must vary according to a thickness of the sheet of paper.
2. Description of the Related Art
In general, an image forming apparatus irradiates light onto a photosensitive medium charged to a uniform potential to form an electrostatic latent image corresponding to a desired image on the photosensitive medium. The image forming apparatus develops the electrostatic latent image using toner to form a toner image, and transfers and fuses the toner image onto a sheet of paper, thereby forming a desired image.
A multi-color image forming apparatus generally requires yellow (Y), magenta (M), cyan (C), and black (B) toners. These color toners overlap each other to exhibit a desired multi-color image. Accordingly, the multi-color image forming apparatus requires four developing cartridges for storing respective color toners.
The multi-color image forming apparatus having the four developing cartridges has a larger volume and a more complicated structure than a monochromic image forming apparatus for exhibiting a single color.
In the image forming apparatus, the sheets of paper in a cassette, in which the sheets of paper are loaded, are sequentially conveyed by components, such as a conveying roller, transfer roller, and fusing unit. Then each sheet of paper is ejected by an ejecting unit outside the image forming apparatus. In structural and economical aspects, these components are driven by a driving source, but are not connected to the respective driving sources. That is, at least one driving source is connected to several components. Accordingly, when one driving source operates, many components connected are simultaneously driven.
For example, assuming that a conveying roller, transfer roller, fusing unit, and ejecting unit connected to one driving motor simultaneously operate, when printing is performed on a general-purpose sheet (for example, an A4 size sheet of paper), the sheet passes through the fusing unit and the ejecting unit at a normal speed. Thus, a toner image transferred onto the sheet can be normally fused on the sheet. However, when printing is performed on a special-purpose sheet (for example, an envelope or film), the time required for fusing a toner image on the special-purpose sheet is longer than the time required for the general-purpose sheet.
Accordingly, when the special-purpose sheet passes through the fusing unit at the same speed as the general-purpose sheet, the toner image may not normally be fused on the sheet. If the toner image is not normally fused on the sheet, image quality is adversely affected.
Accordingly, there is a need for an improved method of varying a fusing speed of an image forming apparatus according to a size of a sheet of paper in order to produce a quality toner image on the sheet of paper.